Fire detectors which can be battery powered or powered with utility supplied AC current are known. Battery powered detectors have become very popular as they are self-contained and can easily be installed almost anywhere. They are usually stand alone devices which do not interact with other similar detectors in the same region or installation.
Detectors which are coupled together by a communications line provide an alternate to stand alone, battery powered units. Such systems usually incorporate a three conductor cable. Two conductors (AC hot and neutral) provide electrical energy to power the detectors. A third conductor is used for signaling between detectors.
The cables terminate in three conductor sockets. A matching plug couples each detector to the cable.
Over a period of time, different socket/plug combinations have been used by manufacturers. In fact, there have been instances where a later model detector would not be compatible with previously installed sockets of the same manufacturer.
The problem of older, previously installed sockets impedes the replacement of older detectors with more current models. Where AC powered, or, interconnected detectors are installed in residences or small businesses, there may not be persons available who can safely remove the existing sockets and replace them with sockets compatible with more current models from the same or different manufacturers.
There is an on-going need to facilitate replacement of older AC powered, or, interconnected detectors with more current models. It would be most desirable if current detectors could be coupled to existing sockets without requiring any rewiring.